Audacity 3.2.0
FFT.h
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1/**********************************************************************
2
3 FFT.h
4
5 Dominic Mazzoni
6
7 September 2000
8
9 This file contains a few FFT routines, including a real-FFT
10 routine that is almost twice as fast as a normal complex FFT,
11 and a power spectrum routine which is more convenient when
12 you know you don't care about phase information. It now also
13 contains a few basic windowing functions.
14
15 Some of this code was based on a free implementation of an FFT
16 by Don Cross, available on the web at:
17
18 http://www.intersrv.com/~dcross/fft.html
19
20 The basic algorithm for his code was based on Numerical Recipes
21 in Fortran. I optimized his code further by reducing array
22 accesses, caching the bit reversal table, and eliminating
23 float-to-double conversions, and I added the routines to
24 calculate a real FFT and a real power spectrum.
25
26 Note: all of these routines use single-precision floats.
27 I have found that in practice, floats work well until you
28 get above 8192 samples. If you need to do a larger FFT,
29 you need to use doubles.
30
31**********************************************************************/
32#ifndef __AUDACITY_FFT_H__
33#define __AUDACITY_FFT_H__
34
35#include <wx/defs.h>
36
38
39/*
40 Salvo Ventura - November 2006
41 Added more window functions:
42 * 4: Blackman
43 * 5: Blackman-Harris
44 * 6: Welch
45 * 7: Gaussian(a=2.5)
46 * 8: Gaussian(a=3.5)
47 * 9: Gaussian(a=4.5)
48*/
49
50#include <wx/defs.h>
51#include <wx/wxchar.h>
52
53#ifndef M_PI
54#define M_PI 3.14159265358979323846 /* pi */
55#endif
56
57/*
58 * This is the function you will use the most often.
59 * Given an array of floats, this will compute the power
60 * spectrum by doing a Real FFT and then computing the
61 * sum of the squares of the real and imaginary parts.
62 * Note that the output array is half the length of the
63 * input array, and that NumSamples must be a power of two.
64 */
65
66MATH_API
67void PowerSpectrum(size_t NumSamples, const float *In, float *Out);
68
69/*
70 * Computes an FFT when the input data is real but you still
71 * want complex data as output. The output arrays are the
72 * same length as the input, but will be conjugate-symmetric
73 * NumSamples must be a power of two.
74 */
75
76MATH_API
77void RealFFT(size_t NumSamples,
78 const float *RealIn, float *RealOut, float *ImagOut);
79
80/*
81 * Computes an Inverse FFT when the input data is conjugate symmetric
82 * so the output is purely real. NumSamples must be a power of
83 * two.
84 */
85MATH_API
86void InverseRealFFT(size_t NumSamples,
87 const float *RealIn, const float *ImagIn, float *RealOut);
88
89/*
90 * Computes a FFT of complex input and returns complex output.
91 * Currently this is the only function here that supports the
92 * inverse transform as well.
93 */
94
95MATH_API
96void FFT(size_t NumSamples,
97 bool InverseTransform,
98 const float *RealIn, const float *ImagIn, float *RealOut, float *ImagOut);
99
100/*
101 * Multiply values in data by values of the chosen function
102 * DO NOT REUSE! Prefer NewWindowFunc instead
103 * This version was inconsistent whether the window functions were
104 * symmetrical about NumSamples / 2, or about (NumSamples - 1) / 2
105 * It remains for compatibility until we decide to upgrade all the old uses
106 * All functions have 0 in data[0] except Rectangular, Hamming and Gaussians
107 */
108
110{
123
124MATH_API
125void WindowFunc(int whichFunction, size_t NumSamples, float *data);
126
127/*
128 * Multiply values in data by values of the chosen function
129 * All functions are symmetrical about NumSamples / 2 if extraSample is false,
130 * otherwise about (NumSamples - 1) / 2
131 * All functions have 0 in data[0] except Rectangular, Hamming and Gaussians
132 */
133MATH_API
134void NewWindowFunc(int whichFunction, size_t NumSamples, bool extraSample, float *data);
135
136/*
137 * Multiply values in data by derivative of the chosen function, assuming
138 * sampling interval is unit
139 * All functions are symmetrical about NumSamples / 2 if extraSample is false,
140 * otherwise about (NumSamples - 1) / 2
141 * All functions have 0 in data[0] except Rectangular, Hamming and Gaussians
142 */
143MATH_API
144void DerivativeOfWindowFunc(int whichFunction, size_t NumSamples, bool extraSample, float *data);
145
146/*
147 * Returns the name of the windowing function (for UI display)
148 */
149
150MATH_API const TranslatableString WindowFuncName(int whichFunction);
151
152/*
153 * Returns the number of windowing functions supported
154 */
155
156MATH_API int NumWindowFuncs();
157
158MATH_API void DeinitFFT();
159
160#endif
MATH_API void InverseRealFFT(size_t NumSamples, const float *RealIn, const float *ImagIn, float *RealOut)
Definition: FFT.cpp:268
eWindowFunctions
Definition: FFT.h:110
@ eWinFuncRectangular
Definition: FFT.h:111
@ eWinFuncBlackmanHarris
Definition: FFT.h:116
@ eWinFuncGaussian25
Definition: FFT.h:118
@ eWinFuncCount
Definition: FFT.h:121
@ eWinFuncGaussian45
Definition: FFT.h:120
@ eWinFuncHamming
Definition: FFT.h:113
@ eWinFuncBartlett
Definition: FFT.h:112
@ eWinFuncBlackman
Definition: FFT.h:115
@ eWinFuncHann
Definition: FFT.h:114
@ eWinFuncWelch
Definition: FFT.h:117
@ eWinFuncGaussian35
Definition: FFT.h:119
MATH_API void FFT(size_t NumSamples, bool InverseTransform, const float *RealIn, const float *ImagIn, float *RealOut, float *ImagOut)
Definition: FFT.cpp:131
MATH_API const TranslatableString WindowFuncName(int whichFunction)
Definition: FFT.cpp:334
MATH_API void DerivativeOfWindowFunc(int whichFunction, size_t NumSamples, bool extraSample, float *data)
Definition: FFT.cpp:538
MATH_API void NewWindowFunc(int whichFunction, size_t NumSamples, bool extraSample, float *data)
Definition: FFT.cpp:370
MATH_API int NumWindowFuncs()
Definition: FFT.cpp:329
MATH_API void PowerSpectrum(size_t NumSamples, const float *In, float *Out)
Definition: FFT.cpp:304
MATH_API void WindowFunc(int whichFunction, size_t NumSamples, float *data)
Definition: FFT.cpp:515
MATH_API void DeinitFFT()
Definition: FFT.cpp:114
MATH_API void RealFFT(size_t NumSamples, const float *RealIn, float *RealOut, float *ImagOut)
Definition: FFT.cpp:230
Holds a msgid for the translation catalog; may also bind format arguments.